No need to remove the window triangle.
It is normal that it is stuck on window part cause there are metal pins that hold the door card to the metal of the door.
Actually the pins hold the rubber strip that is glued to the door card
Try to pry it out with th screwdriver.
The rubber strip will probably fall off in the process but you can glue it back on

You removed all the screews, including the one near the tweeter?

What part of the door card is stuck?

That is strange since there is nothing there that can stuck onto something especially if the rubber strip  next to window is loose from the door card.

Then pry it out with the screwdriver or rather try pushing the whole door card from the bottom up (even carefully hitiing it from the bottom up).
Rubber strip is connected to the door card but never mind if it comes of it can be glued back on (glue is holdin it).
The only thing keeping the door card on the the door should be that rubber strip if all screws are removed.

i'll get my hands on it tomorow and try it again... my old astra ratled but eventualy stopped.. dunno why but i never asked =))